Background: Community-acquired pneumonia (CAP) causes a major burden to the health care system among children under-5 years worldwide. Information on respiratory viruses in non-severe CAP cases is scarce.

Objectives: To estimate the frequency of respiratory viruses among non-severe CAP cases.

Study design: Prospective study conducted in Salvador, Brazil. Out of 820 children aged 2-59 months with nonsevere CAP diagnosed by pediatricians (respiratory complaints and radiographic pulmonary infiltrate/consolidation), recruited in a clinical trial (ClinicalTrials. gov Identifier NCT01200706), nasopharyngeal aspirate samples were obtained from 774 (94.4%) patients and tested for 16 respiratory viruses by PCRs.

Results: Viruses were detected in 708 (91.5%; 95% CI: 89.3-93.3) cases, out of which 491 (69.4%; 95% CI: 65.9-72.7) harbored multiple viruses. Rhinovirus (46.1%; 95% CI: 42.6-49.6), adenovirus (38.4%; 95% CI: 35.0-41.8), and enterovirus (26.5%; 95% CI: 23.5-29.7) were the most commonly found viruses. The most frequent combination comprised rhinovirus plus adenovirus. No difference was found in the frequency of RSVA (16.1% vs. 14.6%; P= 0.6), RSVB (10.9% vs. 13.2%; P= 0.4) influenza (Flu) A (6.3% vs. 5.1%; P= 0.5), FluB (4.5% vs. 1.8%; P= 0.09), parainfluenza virus (PIV) 1 (5.1% vs. 2.8%; P= 0.2), or PIV4 (7.7% vs. 4.1%; P= 0.08), when children with multiple or sole virus detection were compared. Conversely, rhinovirus, adenovirus, enterovirus, bocavirus, PIV2, PIV3, metapneumovirus, coronavirus OC43, NL63, 229E were significantly more frequent among cases with multiple virus detection.

Conclusions: Respiratory viruses were detected in over 90% of the cases, out of which 70% had multiple viruses. Several viruses are more commonly found in multiple virus detection whereas other viruses are similarly found in sole and in multiple virus detection.